A Thread for those interested in PPSL enclosures

[weltersys]

I'm using a 12 inch driver; the approx SD is about 90 square inches and my plenum exit is also 90 sq inches, so is that a 2:1 ? (or does the volume of said plenum come into play somehow?)

DJK's examples compare SD to plenum exit area.

If you are using "a 12 inch driver" the ratio is 1/1 .
If your two drivers total 180 SD, and the plenum exit is 90, the ratio is 2/1.

 

[jdubs]

Guys, can anyone help me out with a PPSL design for the PE 295-120? djk recommended it to me as a good home-system driver with a -3db @ 27hz in the PPSL design with a ~5 cu ft. cabinet. I need to cross it at 300hz and djk indicated this would be no problem. Specs are as follows:

Dayton Audio ST305-8 12" Series II Woofer 295-120

• Power handling: 275 watts RMS/380 watts max • VCdia: 2-1/2" • Le: 3.07 mH • Impedance: 8 ohms • Re: 6 ohms • Frequency response: 25-2,000 Hz • Magnet weight: 56 oz. • Fs: 30 Hz • SPL: 92 dB 1W/1m • Vas: 4.52 cu. ft. • Qms: 10.55 • Qes: 0.36 • Qts: 0.35 • Xmax: 8 mm • Dimensions: Overall diameter: 12", Cutout diameter: 11", Depth: 6", Magnet diameter: 6-1/8", Magnet height: 1-7/8".

I've been trying to get through to djk, but to avail. Anyone that can help, I would very much appreciate it.

Thanks,
Jim

 

[djk]

Driver Properties
Name: 295-120
Type: Standard one-way driver
Company: Dayton Loudspeaker Co.
Comment: Nov 2011 (New)
No. of Drivers = 2
Mounting = Standard
Wiring = Parallel
Fs = 29.6 Hz
Qms = 10.55
Vas = 128.1 liters
Cms = 0.351 mm/N
Mms = 82.29 g
Rms = 1.451 kg/s
Xmax = 8 mm
Xmech = 12 mm
P-Dia = 254 mm
Sd = 506.7 sq.cm
P-Vd = 0.405 liters
Qes = 0.36
Re = 6 ohms
Le = 3.07 mH
Z = 8 ohms
BL = 15.97 Tm
Pe = 275 watts
Qts = 0.348
no = 0.89 %
1-W SPL = 91.64 dB
2.83-V SPL = 92.89 dB
-----------------------------------------
Box Properties
Name:
Type: Vented Box w/ Active HP Filter
Shape: Prism, square
Vb = 4.502 cu.ft
Fb = 27 Hz
QL = 6.24
F3 = 27.1 Hz
Fill = minimal
No. of Vents = 2
Vent shape = rectangle
Vent ends = two flush
Hv = 10 in
Wv = 2 in
Lv = 29.49 in
-----------------------------------------
Active 12 dB/oct. HP Filter
Fx = 27 Hz
Qx = 2

 

[jdubs]

djk! Thanks!! Hugely helpful. Now, just one more favor (not just for me, but the community at large!) Can you do a cut list for a vertically oriented cabinet following these design parameters? Similar to what you did for the PA cabinet, here, but higher than wide (better for most home setups):

http://www.diyaudio.com/forums/subw...nterested-ppsl-enclosures-12.html#post2646368

Seriously, you would then have provided detailed plans for both PA and home system cabinets. This would be great for LOTS of people!

Thank you again.

Jim

 

[anubisgrau]

anything came out of jdubs plea? interested in the same thing, vertical cab for a 12" like the above dayton.

 

[Scott L]

winter build

To my fellow diy'ers: please bear in mind this thread contains a wealth of information. A lot of questions have been asked, answered and then asked again. The most amazing aspect of this thread is, it went off topic by the 3rd post and never agained returned. Even I, as in myself, missed this the first 2 times i read everything on here, in it's entirety. It wasn't until (by coincidence) that I came up with the idea of using a ppsl "motor" as a compression chamber for a mid-bass horn, that i went back (again) and read the beginning, only to see that's what "jamikl" had in mind, in the first place.

Please allow me to re-iterate. This ppsl concept is not as complicated as some would make it out to be. For me, my adaptation of the ppsl principle has given me the exact: accurate, full, punchy and dynamic system I had been seeking for a long time. For my application, it's mid-bass, and the most twisted hybrid style never seen before, but I also plan on doing a conventional in box ppsl woofer system for a 3 way in another project.
My hat's off to djk.

 

[anubisgrau]

wow, the most right pic looks most interesting - PPSL coupled with mid horn, EV's big whale and TPL-150. is this your system scott?

what do you expect to get attaching a front horn there (except maybe to harmonize the crossing and smooth the sound characters from sub/bass and mid-horn)?

 

[Scott L]

yes

wow, the most right pic looks most interesting - PPSL coupled with mid horn, EV's big whale and TPL-150. is this your system scott?

what do you expect to get attaching a front horn there (except maybe to harmonize the crossing and smooth the sound characters from sub/bass and mid-horn)?

Yes, this is my system aka "the beast". The ribbon tweeter is the Stage Accompany SA 8535. I listend to the ppsl motor sans the horn for a while,
but when I added it, the directivity factor increased, as well as the dynamic impact. So, yes, you are correct. This is the best system I have ever had.
Only took 39.5 years of building, and trying different things. Tube amps and horns for me. Having said that, I realize they're not for everybody. For me, this approach allows me to emotionally connect to the peformance.

Not visable in any of the above pics, is the sub-bass system. Mono because of space restrictions/ room layout. 8x AE IB15's in an infinite baffle.50Hz and down to about 17, but I am considering changing up to 60 Hz.

Throw Thiel/Small out the windown when dealing with this type of ppsl. There is strong response down to the mid 30's. I can't expalin why, it just is.
Of special note: the fs of the Eminence Definimax4012HO is 46, but when coupled in the ppsl with the partnering driver, the fs dropped to 40. Then, after I added the sealed back-wave enclosures (which are of differing volumes to compensate for the fact one driver is "flipped") the system resonance (Fc as oppossed to Fs) was @ 57Hz with a Qtc of about .6 if memory serves correct. Stunning, articulate, and dynamic bass with no hint of a "box" sound at all. Highly reccomended.

 

[anubisgrau]

thanx for explaining, though not sure if your approach - ppsl plus extra subs - would be as appealing as ppsl alone - the reason why i'm attracted to this is a promise you can get have a reasonably (!) sized sub/midbass (say 30-300hz) solution. not everyone can afford too much real estate for this hobby...

 

[TMHutson]

I am also curious if using a common enclosure instead of a divided enclosure effects the sound in a positive way on your horn...

I have a question... Most of the people on here have been dealing with large diameter woofers... Does this design work with smaller woofers, such as a 10" in a home/music setting? I also have some 8" subs laying around. I suppose I could just do it with some freebies I have laying around and measure when I can get some equipment to do so. I have seen OB PPSL enclosures that used smaller woofers, but it had at least 6 of them or more due to the low SPL with OB in the lower frequencies...

 

[anubisgrau]

in case one would run these passive and would love to (try) to time align, where would be an acoustic centre in a PPSL cab?

 

[djk]

It seems to be around the back edge of the woofer frame.

It's usually easy to get it within 1/8W of the crossover frequency to a horn mid, or ±11.3" for a 150hz crossover in this system:

http://i56.photobucket.com/albums/g196/dkleitsch/CoePA-2009.jpg

People hearing this system for the first time are shocked by how much visceral impact it has, and are surprised that there is no provision for delay in the crossover network. The system sounds much bigger and more powerful that it actually is.

"Does this design work with smaller woofers, such as a 10" in a home/music setting? I also have some 8" subs laying around. "

I did a dual 8 PPSL for a friend a while back, the drivers were shielded and he used it for a stand for a 19" TV in his basement. It was OK, but with only 60W on it it wouldn't knock things off the walls like he wanted it to. Some higher x-max 8s with more power behind them would have done it, or more 8s.

I made a quad box like this for a car (the ports were a little different than shown):

http://i56.photobucket.com/albums/g196/dkleitsch/1285269007.gif

 

[Scott L]

non common enclosure for my mid-bass

In my case, each woofer sees it's own "volume" of air. The preferred and djk approved method uses a common air volume for both woofers. It's not the first time I have gone against the grain in my life.
Most of the reason why I did this was: I hate wooden boxy sound !
I had built a previous version of a ppsl (using the exact same woofs) that ended in disasterous results. Part of the reason was [that] I had the 2 woofs too far apart physically. So, while back at the drawing board I came up with the next plan, which was to have minimal use of a wooden structure; the volumes of air would be contained by sono-tubes, and the end caps are mutliple/alternating layers of smaller and smaller diameter plywood/mdf.
Thus, there are NO PARALELL surfaces in the enclosure. The two volumes of air are different because of the fact one woofer is flipped. This is probably not ideal, but it worked in my case. I fully intend to build another version of a ppsl in a conventional boxed enclosure (double constrained layers). The next version will use 2@ 15 inchers. Speaking of size, I see no reason why there's a limitation on woofer size. Persoanally, though, i wouldn't go any smaller than an eight inch, because 6 1/2 inches is not a woofer size. Ten inchers might just be the ideal compromise between bass extention and enclosure size. As with any other woofer/or/ sub-woofer system, the lower in frequency one wishes to go requires a bigger and bigger volume. In a ppsl the plenum volume gets added in to the equation. This is why djk has adopted the use of 6th order assisted (equalized) alignments. There has been much discussion on that topic in this thread. I also should mention, since my ppsl's act as compression chambers to load a horn, they are indeed sealed. For a stand alone subwoofer, I'd go the vented route. My conclusion is, the ppsl approach is brilliant. I fully echo Les Hudson's view- I won't waste my time doing any other woofer system other than a ppsl. Pictures show the minimalist use of wood in the motor structure.

 

[Naturlyd]

Useful frequency band?

This looks really good Scott!

How far up in frequency do the PPSL go cleanly? With and without the horn? Any measurements?

 

[TMHutson]

Thanks for the responses. Good to know the separated enclosures work for you!
I was curious on smaller woofers, as I have a bunch laying around. Including some crappy free 10" car subs that were brand new and in the trunk of a car I bought a while back. All the woofers I have are designed for sealed enclosures and don't sim well with ported. I have built sealed, ported and bandpass enclosures. Now I am curious to hear PPSL enclosures in the home.
Now that there is a name that I understand for this type of enclosure design, I now realize I have seen this design around many times in the car audio industry... I had even considered doing free air subs in the trunk sharing a chamber that blows out the arm rest that folds down in the back of my car... I also saw a Kicker competition vehicle in very early 90's. It had a whole bunch of huge woofers facing into a cube port that blew through the rear window in a dually type truck with a topper on it. It was so loud, deep and clean that he couldn't even turn it up more than a couple notches on the volume control. Even with my fingers plugging my ears, it was pretty loud at relatively "low volume" He got pulled over by the police (this was in MN keep in mind) and told to keep it down. He said he had the volume at about 1/4 and didn't get a ticket because it was a demo truck for Kicker. Cab sounded decent as it had tons of drivers in it. I saw the vehicle in the parking lot of a taco bell across the street from where I worked at the time. He was not even showing it off. Just was driving through town after a competition...
So, based on my experience and the experience of others on this thread, I am gunna try one now!

 

[IG81]

This looks really good Scott!

How far up in frequency do the PPSL go cleanly? With and without the horn? Any measurements?

Great thread, I did not really know much about this type of loading before, very interesting.

djk mentioned having the plenum no wider than ¼-wavelenght of the second harmonic for the highest frequency if I understood correctly. This seems to bring the width down to ridiculously small dimensions as soon as you get above upper bass. This would prevent using one driver with the motor in the plenum quickly enough, so would it then be acceptable to flip it back inside the enclosure? In any case, with indirect radiation, I'd not expect this setup to play really high. The EV MTS-1 crosses at 800Hz for a seemingly wide gap, I don't know what's the story there, but it seems like a common place to cross to 2" or the best 1" compressions drivers.

IG

 

[djk]

I got a chance to look at the plenum on the EV, but was not able to measure them or listen to them. The plenum hung down at about a 45° angle so you could see the front of the cone for the top woofer.

The 1/4W of the 2nd harmonic just describes the optimum for 20dB of cancellation, the real limitation seems to be the cavity depth. I have not tried the EV method, so I can't speak to how well it performed. At some point some sawdust will have to be made to see if it will do what you need it to do. My first pair of PPSL were particleboard to keep the cost down.

I have been meaning to make a dual 8 version with the JBL 2118 and mount the drivers so close to each other that the magnet nestles inside the opposing cone. With a slot with a 4:1 compression ratio coupled to a horn I am expecting to be able to push it quite high. Should be interesting.

 

[IG81]

thanks djk

I got a chance to look at the plenum on the EV, but was not able to measure them or listen to them. The plenum hung down at about a 45° angle so you could see the front of the cone for the top woofer.

The 1/4W of the 2nd harmonic just describes the optimum for 20dB of cancellation, the real limitation seems to be the cavity depth. I have not tried the EV method, so I can't speak to how well it performed. At some point some sawdust will have to be made to see if it will do what you need it to do. My first pair of PPSL were particleboard to keep the cost down.

I have been meaning to make a dual 8 version with the JBL 2118 and mount the drivers so close to each other that the magnet nestles inside the opposing cone. With a slot with a 4:1 compression ratio coupled to a horn I am expecting to be able to push it quite high. Should be interesting.

JBL 2118 would make this a midbass/lower-midrange unit I guess? Keep us posted on this if you build it. I checked and the parameters for my Celestion TF1020 midbass drivers are not too far from that JBL, maybe I should get a PPSL in my projects queue. Might be good if I could get strong and clean output in the 60Hz-600Hz decade with these. They currently reside in my DIY Karlson K12 and do well in there.

IG

 

[Scott L]

answers

This looks really good Scott!

How far up in frequency do the PPSL go cleanly? With and without the horn? Any measurements?

Only measured WITH the horn. Side note: I built the horn with materials I already had on hand; I did not want to spend any more money than i already had being this was a "prototype". Therefor this horn is somewhat size compromised. The response is generally flat from 40- 800 Hz, except there is a very gradual rise to a +6db peak at 200Hz, and then it falls back to the flat line until 800 Hz- higher than that it falls off again. I'm using a (gasp!) in-line equalizer to flatten the curve. Someday I'll build a better horn, but right now am just enjoying the music.

Answer to Dennnis ( sorry i don't know how to do a double quote ):
"I have been meaning to make a dual 8 version with the JBL 2118 and mount the drivers so close to each other that the magnet nestles inside the opposing cone. With a slot with a 4:1 compression ratio coupled to a horn I am expecting to be able to push it quite high. Should be interesting."

If you look closely at my above pics, you can see I did indeed that- the drivers are so close the magnet nestles inside the cone. I remember before you instructed me (my last attempt) that my woofers were too far apart, so I went to the other extreme
My plenum slot is 2:1, but the horn throat is then again somewhat smaller, resulting in a compression ratio of about 2.5 :1

I'm happy to see there is shared enthusiasm of adapting the ppsl principle to drive a horn. It's simply the best mid-bass I have ever heard, Beraneck not withstanding.

 

[TMHutson]

I understand the PPSL technique much more than designing a horn (I have trouble with horn design from the calculating aspect). So will be watching this to see what comes of both together!